Yes the silicon tubing helps to prevent the needle valve from sucking air into the fuel stream. As a side effect it prevents the needle from turning as well. Mainly with the tubing in place the detent spring is sort of disabled.

So far on all the Chinese engines I have seen, the needle valve lets air get sucked into the fuel stream, this results in rough running, false needle settings, and poor engine performance obviously.
But some people have been luckier and have gotten engines that worked OK and had decent carbs to start with. Just not me.